I doubt many of those government guns will stay on the job during a real crisis where people shoot back. They will go home to their families in the hopes of defending them just like everyone else will. As far as the military goes... I believe they will be on our side when push comes to shove. If not we will make Afghanistan seem like kindergarten training.
Yet we see stories every day on FR where the police kick doors down at incorrect addresses and shot family pets. Never underestimate the police state....
There's a lot of factors we used to look at in the early, head scratching days of the Iraqi insurgency. Terrain, population density, numbers of fighters, supporters, or fence sitters by percentage, religious and tribal affiliation, education level, military experience, resources, access to weapons, etc.
One of the more interesting things is that we never were fighting all that many Iraqis. They ranked poorly in almost any measurable category. Even the tribal or religious inroads we had made in the various areas didn't get us much play. During one of these think tank meetings I had been suckered into (I was more of a targeting analyst, not a researcher), one of the panelists mentioned offhand how lucky we were this wasn't actually California. The land mass was roughly the same as Cali, and that comparison was common.
It was daunting on an epic scale to imagine all those metrics suddenly rise and max out. If you get anything more than a very tiny percent of the population rise up, it would outstrip what the standing Army could handle very, very fast. Not without taking the gloves off. Which, in counterinsurgency, means that videos of your side doing some ugly clean up work will wind up on the internet, and add 200,000+ enemies. In the media age, a big Army is a bull in a china shop. Anything more than a very tightly controlled movement, and you wind up doing more harm than good at every turn.
Anyway, long story short, you're right. If the average American gun owner rose up at breakfast, Afghanistan on a bad day would look like Kindergarten by lunchtime.